Currently, a touch panel system is rapidly being installed into various electronic equipments including mobile information equipments such as smart phones and vending machines such as automatic ticket machines.
An example of a basic configuration of a conventional touch panel system, as a position inputting device, installed on a display screen of a display device is explained while referring to FIG. 21.
FIG. 21 is a structural drawing of a conventional display device with a position inputting device, having a conventional touch panel system installed as the position inputting device.
In FIG. 21, a conventional touch panel system 100 comprises: a touch sensor panel 101 as a projection-type position inputting device having an electrostatic capacitance; a drive line driving section 110 for generating a state signal of electrostatic capacitance in sense line SL that three-dimensionally intersects with drive lines DL in a plan view by sequentially driving the drive lines DL in the touch sensor panel 101; a touched position detecting section 120 for detecting a touched position that is in contact with or in the proximity of a display screen P by processing a signal for a change in the state signal of electrostatic capacitance generated on the sense lines SL at a position where the drive lines DL are driven by the drive line driving section 110, and a host terminal 105 for controlling the drive line driving section 110 and the touched position detecting section 120. FIG. 21 illustrates a case in which the drive lines DL and the sense lines SL vertically and intersect with each other in a plan view. However, the lines may intersect in a plan view at an angle other than orthogonal.
The touch sensor panel 101 is provided on the display screen P of a liquid crystal panel. Further, the touch sensor panel 101 is provided with a plurality of parallel drive lines DL provided for each predetermined interval along the display screen P of the liquid crystal panel, and a plurality of parallel sense lines SL which intersect in a plan view with the drive lines DL provided along the display screen P for each predetermined interval. An electrode for detecting capacitance is provided for each line. The drive lines DL and the sense lines SL are made of, for example, a transparent material.
The touched position detecting section 120 comprises: an amplifying circuit 121 for amplifying a state signal of electrostatic capacitance generated on the sense lines SL; a signal obtaining section 122 for obtaining the state signal of electrostatic capacitance amplified by the amplifying circuit 121 for outputting the signal in a time division; an A/D converting section 123 for converting an analog signal outputted by the signal obtaining section 122 to a digital signal; a decoding section 124 for finding the amount of change in a capacitance distribution within the display screen P based on the digital signal converted by the A/D converting section 123; and a touched position calculating section 125 for calculating a touched position on the display screen P based on the amount of change in the capacitance distribution found by the decoding section 124 to generate touched position information indicating the touched position.
The host terminal 105 controls the drive lines DL driven by the drive line driving section 110. Further, the host terminal 105 controls the sense lines SL for processing a state signal of electrostatic capacitance by the touched position detecting section 120 via the drive lines DL.
FIG. 22 is a partially enlarged plan view of a touch panel showing an example of a shape of electrodes of the drive lines DL and sense lines SL of FIG. 21.
As shown in FIG. 22, the following are formed on the touch panel 101: a drive line electrode pattern 102 comprising a plurality of rhombus shaped large-area pad sections that extend in a first direction shown by arrow Y, where a plurality of the patterns are arranged in a second direction shown by arrow X; and a sense line electrode pattern 103 comprising a plurality of rhombus shaped large area pad sections that extend in a second direction shown by arrow X, where a plurality of the patterns are arranged in the first direction shown by arrow Y to intersect (herein, orthogonally) with the drive lines DL.
When the drive lines DL are sequentially driven by the drive line driving section 110, a state signal of electrostatic capacitance is generated in the sense lines SL that intersect the drive lines DL in a plan view. The state signal is a signal indicating the state of electrostatic capacitance at a touched position on the above-described intersecting section in a plan view or a section in the proximity within the display screen P (hereinafter, referred to as detection region A).
The state signal would have a value corresponding to electrostatic capacitance produced between the drive lines DL and the sense lines SL. Such a signal indicates whether there is contact or proximity to the detection region A within the display screen P. e.g., the presence of a contact or proximity to the detection region A or separation distance between the detection region A and a pointer. Electrostatic capacitance becomes smaller when in contact with or in the proximity of the detection region A.
Next, an example of a basic operation of the conventional touch panel system 100 is explained with the configuration described above. Herein, a single run operation is explained, where the touch panel system 100 detects a touched position in contact with or in the proximity of the display screen P.
First, the drive line driving section 110 sequentially drives the plurality of drive lines DL so that a state signal of electrostatic capacitance is generated in the sense lines SL.
Next, the amplifying circuit 121 amplifies the state signal of electrostatic capacitance generated in the sense lines SL.
Subsequently, the signal obtaining section 122 outputs the state signal of electrostatic capacitance amplified by the amplifying circuit 121 in a time division while matching the timing of driving by the drive line driving section 110. The operational timing of each of the drive line driving section 110, amplifying circuit 121 and signal obtaining section 122 is controlled by the host terminal 105. Specifically, the sense lines SL for processing a state signal of electrostatic capacitance is controlled via the drive lines DL to be driven.
The A/D converting section 123 then converts an analog signal output by the signal obtaining section 122 to a digital signal with a predetermined number of bits.
Furthermore, the decoding section 124 finds the amount of change in a capacitance distribution within the display screen P based on the digital signal converted by the A/D converting section 123. For example, the decoding section 124 obtains a digital signal when a touch subject is not present on the display screen P, prior to the detection of a touched position, to find in advance a capacitance distribution when a touch subject is not present on the display screen P. The decoding section 124 obtains a digital signal upon detection of a pointer to find a capacitance distribution and compares the distribution to the capacitance distribution, which was found in advance for a case where a touch subject is not present, to find the amount of change in the capacitance distribution (amount of change in electrostatic capacitance due to a touch subject).
The touched position calculating section 125 calculates a position of a touch subject on the display screen P based on the amount of change in the capacitance distribution found by the decoding section 124 to generate touched position information. For example, the touched position calculating section 125 determines that a touch subject is present at a section where the amount of change in electrostatic capacitance within the display screen P is large beyond a detection threshold and calculates the position of the touch subject on the display screen P. The touched position calculating section 125 may generate touched position information indicating that calculation could not be performed when a position of a touch subject cannot be calculated.
In the conventional touch panel system 100 of this specific example, position detection of a touch subject is continuously run by repeating the aforementioned run operation.
The host terminal 105 controls each of the drive line driving section 110 and the touched position detecting section 120 while referring to the touched position information output by the touched position calculating section 125 as needed. Further, the host terminal 105 controls the frame rate, which is the number of detections of a touch subject run per unit time (e.g., one second) in touch subject detection.
As stated above, in the basic example of the touch panel system 100 shown in FIG. 21, each of the drive lines DL to be driven by the drive line driving section 110, the sense lines SL for processing a state signal of electrostatic capacitance by the touched position detecting section 120 via the drive lines DL, the frame rate, the detection threshold (detection sensitivity) and the like can be optionally set by the host terminal 105 control.
As described above, the touch panel system 100 detects the amount of change in a sense line capacitance distribution to detect a touched position.
Meanwhile, as the touch sensor panel 101 becomes larger, the amount of computation to find a touched position increases so that consumed power and associated devices, such as an amplifier, tend to be large. Thus, there is a need to keep power consumption and the size of associated devices small.
In this regard, Patent Literature 1, it is possible to keep power consumption and size of associated devices small by sampling scanning to reduce the amount of processing for a common two-dimensional sense pattern.